Marine Aquatic Biomes - Online Tutor, Practice Problems & Exam Prep

The intertidal zone is a dynamic coastal area between high and low tides, where organisms have adapted to survive fluctuating conditions. The marine pelagic zone, or open ocean, covers three-quarters of Earth's surface, exhibiting varying productivity due to depth gradients in sunlight, oxygen, biomass, and nutrients. Coral reefs, formed by calcium carbonate exoskeletons, are biodiversity hotspots in warm, shallow waters. The marine benthic zone, the ocean floor, is nutrient-rich due to decomposing matter, supporting unique ecosystems, including those near hydrothermal vents.

Intertidal Zones

This video, we're going to talk about intertidal zones as aquatic biomes. And so you might recall from our previous lesson videos that we already defined the intertidal zone when we talked about the zonation of marine biomes. And so recall that the intertidal zone can be defined as the coastal shore area that's between the low and high tides. The intertidal zone experiences a wide variation of conditions, as during the low tide, the entire intertidal zone is completely exposed to the air in the atmosphere. But during the high tide, the entire intertidal zone is completely submerged by ocean water, And so the organisms that live in the intertidal zone have evolved adaptations to be able to survive in those different conditions.

And this periodic exposure to air and submersion by ocean water occurs about twice a day as the tides occur about twice in a period of 24 hours. And, the oxygen and nutrient levels can actually be replenished with each high tide. Some intertidal zones will look more like these sandy beaches, and other intertidal zones will look more like these rocky shores. And the aquatic productivity in these intertidal zones actually varies. And in these tidal pools, there can be specific species of fish that are living in there, and these fish may rely on the nutrients and oxygen levels of this tide pool.

And so with each high tide, this entire rocky area could be completely submerged by water, and that submersion kind of moves the water around, replenishes the nutrients, and helps to redistribute the oxygen in those pools to replenish the oxygen. And so this here concludes our brief lesson on intertidal zones.

Marine Pelagic Zone

This video, we're going to talk about the marine pelagic zone as an aquatic biome. And so the marine pelagic zone is also known as the open ocean, and it consists of the entire ocean from the surface down to just above the ocean floor. And so you might recall from our previous lesson videos when we talked about the zonation of marine biomes that we already defined the pelagic zone as the nearshore shallower idic zone plus the offshore deeper oceanic zone. And so this makes the marine pelagic zone the largest biome on earth by far as it's found in all of the world's oceans, and it covers about 3 quarters of the earth's entire surface. Now interestingly enough, the aquatic productivity of the marine pelagic zone actually varies, and this is because of how vast the marine pelagic zone is.

It is enormous. Now what you'll also notice is that here we're showing you a bunch of different gradients that exist with the depth of the ocean water. And so, the first gradient that we have here on the far left is a sunlight gradient, and so there is high sunlight towards the surface. But as you go deeper and deeper into the ocean water, the amount of sunlight gets lower and lower, and eventually, you'll get to an area that's characterized by complete darkness. Now the next gradient that we have here is an oxygen gradient, and it is also going to be a decreasing gradient with depth.

And notice the next gradient that we have is for biomass. Again, it's a decreasing gradient. But interestingly enough, notice that this last gradient is a nutrient gradient. It actually increases with depth, unlike the other three gradients that we just talked about. And the reason for this is because the biomass that's at the surface of the water, when it dies, the dead decaying matter will tend to sink to the bottom of the ocean, and along with it, it will bring nutrients.

And so here, what we're saying in the text is that, generally, there's a decreasing biomass gradient that exists with depth, but there's an increasing nutrient gradient that exists with depth, and that's exactly what we just talked about here. So this here concludes our brief lesson on the marine pelagic zone.

Coral Reefs

This video, we're going to talk briefly about coral reefs. Coral reefs are ridges formed by the calcium carbonate exoskeletons of corals, specifically coral polyps, which are aquatic animals that secrete calcium carbonate, or CaCO3. Over time, the calcium carbonate builds up to form complex and sturdy exoskeletons, giving the coral reef its detailed shape, as shown here in this image. Coral reefs are located in shallow, warm waters found in tropical and subtropical waters. This image shows little red circles representing the locations of coral reefs throughout the world.

Coral reefs are among the most diverse and productive ecosystems on Earth. They have the highest biodiversity of all aquatic biomes, earning them the nickname "rainforests of the sea." Coral reefs are delicate and sensitive, requiring very specific conditions to thrive. It's important for us to be conscious and aware of this so we can protect these delicate and crucial aquatic biomes. This concludes our brief lesson on coral reefs.

Marine Benthic Zone

This video, we're going to talk about the marine benthic zone. Recall that the benthic zone consists of the entire ocean bottom or the entire ocean floor regardless of how shallow or how deep it is. You can think that the 'b' in benthic zone is for the 'b' in bottom. Now, again, much of the benthic zone is going to fall in shallow areas that receive plenty of sunlight. However, because most of the ocean falls in the deeper oceanic zone, most of the benthic zone is going to fall so deep under the ocean surface that it receives very little to no sunlight.

That is going to severely limit the primary production as photosynthesis cannot occur without sufficient amounts of sunlight. However, it is important to keep in mind that there can be deep-sea hydrothermal vents in some parts of the marine benthic zone that can provide a unique source of chemical energy that some specialized organisms can take advantage of and provide some primary production. Now, the marine benthic zone is going to be a nutrient-rich zone, and the reason for that is because there's lots of biomass in the more productive surface waters. When that life dies, it will actually sink towards the bottom, and it will bring along with it the nutrients. The nutrient-rich benthic zone is due to the decomposing dead organisms called detritus that fall to the sea floor, and sometimes this trickling down of the nutrients is referred to as the marine snow effect.

And so this concludes our brief lesson on the marine benthic zone, and we'll be able to get some practice applying these concepts as we move forward. I'll see you all in our next video.

Marine Aquatic Biomes Example 1

So here we have an example problem that asks, which of the following marine biomes could experience turnover in the spring and fall? And we've got these 4 potential answer options down below. Now, of course, recall from our previous lesson videos that turnover refers to seasonal turnover, and seasonal turnover refers to the vertical mixing of waters in a lake or an ocean specifically during the spring and fall seasons. Recall that the vertical mixing of waters is driven by changes in the density of the water as the temperature of the water changes from season to season. And so, because turnover refers to the vertical mixing of waters, we're looking for a marine biome that has sufficient amounts of water for there to be vertical mixing.

Notice that answer option c says, coral reefs, but coral reefs themselves are not going to experience turnover because the coral reef is not water, the coral reef is those rigid calcium carbonate exoskeletons formed by the coral polyps. So, they don't experience turnover, we can eliminate option c. Now option d says the marine benthic zone, and that refers to the bottom of the ocean floor. It's literally just the floor, but it's not referring to the water actually, it's just the floor. Hence, the floor itself does not experience turnover, that's not going to involve vertical mixing, so we can eliminate answer option d.

Now, option b says, intertidal zone, but the intertidal zone is going to be quite shallow and not have a whole lot of water to begin with, so it's not going to have a sufficient amount of mixing, due to turnover, it's not going to experience turnover. So for that reason, we can eliminate option b, and this leaves answer option a as the only option, which is the best choice here, the pelagic zone. Recall that the pelagic zone includes both the nearshore neritic zone and the offshore oceanic zone, and so it's basically all of the water in the open ocean. And so, the open ocean, in some areas, under the right conditions, can experience some amounts of turnover. And so that's why option a is the correct answer to this example. That concludes this problem, and I'll see you all in our next video.

In which marine biome would you expect to find organisms that are adapted to withstand extremely high temperatures & a complete lack of sunlight?

• A. Pelagic zone.
• B. Intertidal zone.
• C. Coral reefs.
• D. Marine benthic zone.

Which of the following marine zones experiences the most fluctuation in temperature?

• A. Pelagic zone.
• B. Intertidal zone.
• C. Neritic zone.
• D. Photic zone.